Existing Third Generation Partnership Project (3GPP) systems, including 2G/3G systems and the newly emerging SAE/LTE system, support the possibility to trace a particular user throughout its lifetime in the network. The users may be selected for tracing based on user identity (International Mobile Subscriber Identity (IMSI)-based trace), terminal identity (International Mobile Equipment Identity (IMEI)-based trace), or location (cell trace). During tracing, all network activities related to the particular user can be logged and later delivered to a central management entity for evaluation. Logged network activities include signaling messages sent/received either on the radio interface or network node interfaces. Additional details of trace functionality in 3GPP systems may be obtained from 3GPP TS 32.421, “Subscriber and equipment trace: Trace concepts and requirements”; 3GPP TS 32.422, “Subscriber and equipment trace: Trace control and configuration management”; and 3GPP TS 32.423, “Subscriber and equipment trace: Trace data definition and management”.
Typically, tracing is utilized to troubleshoot problematic user connections (for example, in response to user complaints) or to monitor generic network performance and to perform root cause analysis to identify network problems.
More recently, 3GPP has started to work with the concept of UE-based network performance measurements (also called Minimization of Drive Test (MDT) measurements), where the objective is to utilize the measurements performed by the terminals for network performance monitoring and optimization purposes. There are MDT measurements defined both for UE connected state and idle state. The connected mode measurements are also called immediate MDT measurements, referring to the fact that the UE reports the measurements as they are performed via the legacy Radio Resource Control (RRC) protocol mechanisms, i.e., no internal logging in the UE. The idle mode MDT measurements are also called logged MDT, because the UE collects and logs the measurements and then reports them to the network in a batch. Note that logged reporting in idle mode is necessary because the UE does not have an active connection to the network in idle mode and thereby it cannot report the measurements at the time they are taken.